Civil Engineering Reference
In-Depth Information
All nuclear components of the reactor core and the components of the cooling
system are designed with high safety margins and must meet stringent requirements
with respect to the choice of materials and the quality of manufacture (e.g., basic
safety, leak-before-break criterion). In-service inspections and, if necessary,
replacement of the components as well as great care in plant operation must ensure
a high standard of technical safety quality throughout the entire operating life. This
is required to make malfunctions extremely unlikely.
Basic rules in technical safety must be applied such as the failsafe principle,
redundant design of cooling systems and safety systems, as well as the principle of
diversity to avoid common-mode failures.
More details are given in Sect.
5.6
.
5.3.2.2 Second Safety Level: Measures of Accident Prevention
Measurement and detection systems (instrumentation), control, monitoring and
limiting systems (e.g. for temperatures, power, pump speeds, pressures, etc.)
prevent accidents by early detection of malfunctioning. Limiting and control
systems take credit of inherent safety properties to counteract disturbances in an
adequate way. After correction of the malfunction, continued operation of the
nuclear power plant is easily possible. Even in such cases of malfunction, the
release levels for radioactive substances permitted in normal operation must not
be exceeded.
More details are discussed in Sect.
5.6.3
.
5.3.2.3 Third Safety Level: Design Basis and Measures to Limit
Accident Consequences
As the occurrence of an accident cannot be completely excluded, nuclear power
plants are equipped with safety systems. These safety related systems include, e.g.,
the reactor protection and shutdown system, the emergency cooling system and
residual heat removal system, and the containment. After having been initiated by
the reactor protection system, the safety systems operate largely automatically so as
to meet the goals of protection referred to above (Sect.
5.2
) and limit the damage
arising from an accident. The design takes into account that one redundancy level of
the safety system may be under repair and another system may not be available
upon request (n + 2 principle) [
4
,
5
].
The plant must accommodate a number of design basis accidents which must be
proved by analysis during the licensing procedure of the reactor plant (Sect.
5.4
).
More details are discussed in Sect.
5.6.6
.
